strength evaluation of laterite soil stabilized …...stabilization using polymer fibers extracted...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 2, February 2018, pp. 227–234, Article ID: IJCIET_09_02_022 Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=2 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication Scopus Indexed

STRENGTH EVALUATION OF LATERITE SOIL

STABILIZED USING POLYMER FIBERS

Jeeja Menon

Research Scholar, Noorul Islam University, Kanyakumari, Tamil Nadu, India

Dr. M. S. Ravikumar

Principal, PSN Engineering College, Tirunelveli, Tamil Nadu, India

ABSTRACT

Stabilization of soil using fibers is one of the effective techniques to improve the

strength of soils and thereby increasing its load bearing capacity making it more

appropriate in the manufacture of compressed stabilized earth blocks (CSEB). This

paper aims to evaluate the strength of locally available laterite soil stabilized using

available fiber as stabilizer, which is classified as clayey silt. The performance of

Polyethylene Terephthalate (PET) bottle fibers and Polypropylene (PP) sack fibers

are separately analyzed for its impact on the unconfined compressive strength of the

soil. Tests were conducted on various fiber-soil ratios in four percentage levels such

as 0, 0.10, 0.15 and 0.2 to determine the optimum fiber content. The experimental

analysis suggests that laterite soil stabilized with optimum PP (sack) fiber content

provides better performance than the laterite soil stabilized with optimum PET (bottle)

fiber content. The results indicate that, the Polypropylene sack fibers are more

optimal and efficient stabilizer for the laterite soil and were selected as the constituent

for developing CSEBs. This study also contributes to effective soil waste management

as a befitting sustainable technique to solve current environmental crisis as well.

Keywords: Compressed Stabilized Earth Blocks (CSEB), Unconfined Compressive Strength, Polyethylene Terephthalate (PET), Polypropylene (PP), Bottle Fibers, Sack Fibers

Cite this Article: Jeeja Menon and Dr. M. S. Ravikumar, Strength Evaluation of Laterite Soil Stabilized Using Polymer Fibers, International Journal of Civil Engineering and Technology, 9(2), 2018, pp. 227–234. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=2

Jeeja Menon and Dr. M. S. Ravikumar


1. INTRODUCTION

Earthen building materials with less embodied energy like adobe, rammed earth and CSEB are experiencing a renaissance in their application as a sustainable building material. The main advantageous of earthen materials over other building materials includes availability of local soil, easiness in construction and their insulating properties [10]. However, soil must be stabilized to improve their geotechnical properties before its application in buildings. Soil stabilization is emerging as a popular and cost-effective technique for enhancing the engineering properties of soil with the availability of enhanced research and equipment. [27]. Stabilization using fiber material is considered as an effective technique among various soil stabilization techniques. The main advantages include its cost effectiveness and easy adaptability. Natural fibers like coconut, sisal, palm and barley were used in the earlier research on soil stabilization. However, these fibers together with their degradability, low strength, low tenacity and low resistance to water absorption, make them less durable as a

stabilization material. [29]. Hence the possibility of using polymer fiber, a type of macromolecule material with high durability, strength, non-degradability and chemical corrosion resistance is being researched as an alternative material for soil stabilization [2].

The potential of using plastics as aggregate and as crack arrester in concrete has been vastly researched during the last two decades [16]. However, past literature indicates that the potential of using polymer fibers in soil stabilization is less researched. Hence the soil stabilization using polymer fibers extracted from waste bottles and sacks has been selected as the area of research. Moreover, disposal of waste plastics has become a grave problem and its utilization as a stabilizer will reduce its detrimental effect on environment [11,18]. In addition to the contribution of this method to the solid waste management it has economic and environmental benefits also. [11,18]

Laterite soils which are widespread in tropical areas of India possess unique color and it normally contains high clay content along with inert particles such as silt and sand [1]. It is widely used to produce earth blocks, but stabilization is essential for the lateritic soil block to enhance its properties. The most commonly used stabilizer is cement which is an energy intensive material and it also produces greenhouse gases during its production. Polymer fibers extracted from waste bottles and sacks are less energy intensive materials. The aim of this paper is to investigate the potential of using Polyethylene Terephthalate (PET) fibers from bottles and Polypropylene (PP) fibers from sacks to stabilize laterite soil, which is used to develop compressed stabilized earth blocks.

2. LITERATURE SURVEY

Literature review reveals that there is a growing interest in the development of stabilized earth building materials like CSEB. Utilization of natural fibers as soil reinforcement has been recognized as an efficient method of soil stabilization from ancient times. [13]. However, this method is becoming unpopular due to the lower strength and durability of natural fibers. Thereafter plastic fiber based stabilization is becoming popular due to its high strength and low cost. The Polyethylene Terephthalate (PET), Polyvinyl chloride (PVC) and Polypropylene (PP) are the mostly researched plastic fiber materials for soil stabilization. These are readily available in usage products like plastic sacks, plastic bottles etc. This stabilization method will also contribute to the solid waste management, which is one of the current foremost environmental concerns in our country.

Research studies have reported that plastic waste fibers increase significantly both UCC and ductility of the stabilized clay soil. [20,13, 21,28]. Even though the soil stabilized with chemical additives like cement show significant improvement in compressive strength, from

Strength Evaluation of Laterite Soil Stabilized Using Polymer Fibers


the stress strain response of the stabilized soil it is observed that higher strength is obtained at a lower strain. This characteristic of soil may be improved by means of incorporation of fibers. It is observed that the post peak stress is reached gradually when fibers are incorporated in the soil and there is a smaller loss of post - peak strength. These two factors will contribute to the increased ductility of the stabilized soil. [20] It is also observed that aspect ratio and fiber content remaining the same, roughness of fibers will influence the strength parameter. [22]

Researchers have observed that the MDD of the plastic fiber stabilized soil decreases due to the low specific gravity of the plastic fibers and O.M.C increases with stabilization. [15]

3. METHOD AND MATERIALS

3.1. Method

The virgin soil properties of the locally available laterite soil is determined by conducting various tests like Grain Size Distribution , Atterberg`s Limits , Specific Gravity , Standard Proctor Test ,Unconfined Compressive Strength Test .Then the soil is separately mixed with Polyethylene Terephthalate( PET) bottle fibres and Polypropylene (PP) sack fibers in three percentage levels 0.10, 0.15 and 0.2 and various tests are conducted to study the effect of fibers on the properties of the soil. The optimum bottle fiber content and optimum sack fiber content is determined based on the unconfined compressive strength of the fiber-soil composition. Comparing the results optimum fiber composition is suggested for the preparation of CSEB.

3.2. Materials

3.2.1. PET (Bottle) Fiber

In this work the PET fibers extracted from used water bottles made by the company ‘Aquafina’ is used. The bottles are cut into sheets after discarding its neck and bottom. Prasad et all suggested that making the surface of the bottle rough will provide more frictional resistance to fibers. Therefore, the sheets are roughened and sliced in the dimension 1.5cm length and 2mm width using the machine specially designed for this which is shown in Figure 1(a) & Figure1(b)

Figure 1 (a) Roughening sack sheets Figure 1 (b) Cutting Bottle Fibers Sample



3.2.2. PP (Sack) Fiber

In this work the polypropylene (PP) fibers extracted from the sacks of leading cement manufacturer ‘Ramco’ is used. The sack is cut into pieces and is roughened using the machine before it is sliced in the dimension of 1.5cm length and 2mm width.

3.2.3. Laterite Soil

In this experiment laterite soil which is classified as clayey silt collected from Perinthalmanna, Kerala, India is used. The soil properties determined are mentioned in the Table 1.

Table 1 Properties of Laterite Soil

Property Value

Natural Water Content (%) 20.4

Specific Gravity 2.54

Optimum Moisture Content (%) 24.02

Maximum Dry Density (g/cc) 1.552

Liquid Limit (%) 57.63

Plastic Limit (%) 38.72

Plasticity Index (%) 18.91

Shrinkage Limit (%) 28.03

Unconfined Compressive Strength (kg/cm2) 0.24

Soil classification Medium Plasticity

Particle size distribution Clay (%) 27

Silt (%) 21

4. TESTING OF FIBER SOIL COMPOSITION

The tests conducted to evaluate the performance of fiber-soil composition are Proctor Compaction Test, Atterberg’s Limits, and Unconfined Compressive Strength Test.

4.1. Light Compaction Test

The light compaction test is carried out to determine the optimum moisture content of the fiber soil composition at which it will attain its maximum dry density. The light compaction test is conducted as per IS 2720(X):1991 Methods of test for Soils.

4.2. Compressive Strength Test

Unconfined compressive strength test is used to measure shear strength. The sample for unconfined compressive strength is prepared by mixing the soil with optimum moisture content. The samples are enveloped in zip cover and the cover is immersed in water contained in a bucket to prevent the loss of moisture from the sample and to maintain constant temperature and humidity. The samples are tested at 0th day, 1st day and 7th day. The test is conducted as per IS 2710 Part 10



Stage 1 Stage 2 Stage 3

Figure 2 Different Stages of Curing

5. RESULTS AND ANALYSIS

5.1. Light Compaction Test

5.1.1. Variation of OMC with fiber content

For both PET bottle and sack fibers, OMC does not vary much with the addition of fibers. It slightly decreases with increase in fiber content in soil.

Figure 3 Variation of OMC with different percentages of fibers

5.1.2. Variation of MDD with fiber content

For both bottle and sack fibers there is a slight increase in maximum dry density up to a fiber content of 0.1% and then it slightly decreases.



Figure 4 Variation of MDD with fiber content

5.2. Unconfined Compressive Strength

The strength of the UCC sample was determined in different percentages (0%, 0.1%, 0.15%, and 0.20%) of fiber in different curing periods (0day, 1day, 7days). Unconfined Compressive Strength of PET bottle fibre soil composition is highest at a fibre content of 0.1% and Unconfined Compressive Strength of PP sack fibres soil composition is highest at a fibre content of 0.15%. In addition, Unconfined Compressive Strength of 0.15% PP sack fibre soil composition is higher than Unconfined Compressive Strength of 0.1% PET bottle fibre soil composition, which implies that PP sack fibre is a better stabilizer than PET bottle fibre. It is also observed that Unconfined Compressive Strength increases with increasing curing periods.

Figure 5 Unconfined Compressive Strength of bottle Fibres

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.1 0.15 0.2

ST

RE

NG

TH

(M

Pa)

PERCENTAGE OF PET FIBRES (%)

UNCONFINED COMPRESSIVE STRENGTH

0TH DAY

1ST DAY

7TH DAY



Figure 6 Unconfined Compressive Strength of Sack Fibers

6. CONCLUSION

The usage of plastic fibers for the stabilization of soil is a recently developed technique which needs research evaluation. This paper reports the stregth enhancement of locally available laterite soil using PET Bottle fibers and PP Sack fibers as stabilizer which can be applied in the manufacture of CSEB. The experimental analysis was conducted at four percentages of fiber content i.e. 0%, 0.10%, 0.15% and 0.2%. Based on the test results it was found that the soil stabilized with 0.15% PP (sack) fibers provided better performance. The strength decrease of bottle fibers may be due to the stiffness imparted by it. Moreover, the bottle fibers are likely to slip during compaction when compared to sack fibers. Therefore, the study suggests that 0.15% PP(sack) fiber is the most suitable stabilizer for laterite soil which is to be used for making compressed stabilized earth blocks.

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strength evaluation of laterite soil stabilized …...stabilization using polymer fibers extracted...

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